CN108460224B - Method for determining length size of indoor combustible gas constraint explosion venting numerical calculation domain - Google Patents
Method for determining length size of indoor combustible gas constraint explosion venting numerical calculation domain Download PDFInfo
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Abstract
The invention discloses a method for determining the length and the size of an indoor combustible gas restraint explosion venting numerical calculation domain, which comprises the steps of firstly, acquiring explosion overpressure experimental data with the size similar to that of a numerical research model through experiments or literature investigation; establishing a physical model of the restricted explosion venting by using numerical simulation software, and designing calculation domains with different length sizes for carrying out numerical analysis; carrying out numerical simulation to obtain relevant explosion overpressure experimental data; comparing the data results to obtain the length size of the calculation domain when the relative error is minimum; determining the length dimension l of an external calculation domain of the explosion venting port according to the length dimension of the calculation domainoutAdding the length dimension L of the room to be studied to obtain the length dimension L of the whole calculation domainout+ l. The determination method can provide reference basis for selection of the length and the size of the calculation domain during gas explosion numerical simulation and acquisition of an accurate explosion venting flow field, thereby improving the prevention and control capacity of indoor gas explosion disasters.
Description
Technical Field
The invention relates to the technical field of combustible gas restraint explosion venting research, in particular to a method for determining the length size of an indoor combustible gas restraint explosion venting numerical calculation domain.
Background
At present, combustible gases such as natural gas, hydrogen and the like have wide application, are industrial raw materials, and can be used as fuel to provide energy for production and life of people. However, when these combustible gases leak, the explosive premixed gas formed by mixing with air is likely to cause explosion accidents when it meets a heat source or a spark, and accidents related to the leakage and explosion of combustible gases sometimes occur. When a combustible gas explosion accident occurs in a civil building or an industrial factory building, doors, windows and light walls usually form a typical constraint explosion venting structure, so that a constraint explosion venting disaster effect is induced. The research on the explosion venting disaster effect of the combustible gas in the limited space is helpful for knowing the law of the explosion venting flow field and improving the prevention and control capacity on the indoor gas explosion disaster, so that a great deal of research is carried out on the restrained explosion venting disaster effect of the combustible gas in the limited space by the scholars.
Because large-scale explosion venting experiments are difficult and low in safety, many scholars adopt a Computational Fluid Dynamics (CFD) technology to carry out numerical calculation on an explosion flow field. When the numerical method is adopted to research the confined explosion venting of the combustible gas, the influence of the size of the external calculation domain of the explosion venting port on the explosion effect needs to be considered, and the influence of the size of the explosion venting port in the length direction on the explosion venting effect is the largest. When the length size of the calculation domain outside the explosion venting port is determined, if the length size is too small, explosion flow field data cannot be completely acquired, and if the length size is too large, calculation time is increased, so that unnecessary waste is caused. Therefore, the rapid and effective determination method of the numerical calculation domain is provided for the indoor combustible gas constraint explosion venting process, which is beneficial to improving the accuracy and scientificity of the research and has important significance for the numerical research process of the combustible gas constraint explosion venting.
Disclosure of Invention
The invention aims to provide a method for determining the length dimension of a calculation domain of an indoor combustible gas restraint explosion venting numerical value, which can provide reference basis for selection of the length dimension of the calculation domain during gas explosion numerical simulation and acquisition of an accurate explosion venting flow field, thereby improving the prevention and control capability of indoor gas explosion disasters.
The purpose of the invention is realized by the following technical scheme:
a method for determining the length size of an indoor combustible gas constraint explosion venting numerical calculation domain comprises the following steps:
The explosion overpressure experimental data comprises:
peak overpressure in the chamber, maximum oscillation amplitude on the overpressure curve, overpressure curves at different locations, peak overpressure in the chamber, and flame speed.
In the step 2, the process of establishing the constrained explosion venting physical model specifically comprises the following steps:
the physical model of the room to be studied is set as a cuboid, the dimensions of which are expressed as:
in the formula, MroomRepresenting the dimensions of the physical model of the room; l represents the length of the room; w represents the width of the room; h represents the height of the room;
the computational domain size is then expressed as:
in the formula, McomputationRepresenting a computational domain size; loutRepresenting the size of a calculation domain outside a room explosion vent; w represents the width of the computational domain; h denotes a computational domainOf (c) is measured.
In step 4, comparing the data result obtained in step 3 with the data result obtained in step 1, and obtaining the calculated domain length size with the smallest relative error specifically includes:
obtaining indoor peak overpressure in different calculation domains according to the numerical simulation result, comparing the indoor peak overpressure with the indoor peak overpressure obtained in the step 1, checking relative error distribution of each group of data and the experiment result, and selecting a proper external calculation domain length size S1;
obtaining maximum oscillation amplitude values on the overpressure curve in different calculation domains according to the numerical simulation result, comparing the maximum oscillation amplitude values with the maximum oscillation amplitude values obtained in the step 1, checking the relative error distribution of each group of data and the experiment result, and selecting a proper external calculation domain length size S2;
acquiring overpressure curves in different calculation domains according to the numerical simulation result, comparing the overpressure curves with the overpressure curves obtained in the step 1, checking whether the oscillation effect on each group of data overpressure curves sufficiently shows the external aerodynamic effect, and selecting a proper external calculation domain length size S3;
obtaining peak overpressure curves near the explosion venting port in different calculation domains according to the numerical simulation result, comparing the peak overpressure curves with the peak overpressure curve obtained in the step 1, checking whether the peak overpressure curves calculated by each group of numerical values tend to be stable along with the increase of the size of the calculation domain, and selecting a proper length size S4 of the external calculation domain;
and (4) acquiring flame speeds in different calculation domains according to the numerical simulation result, comparing the flame speeds with the flame speed acquired in the step 1, and selecting a proper length size S5 of the external calculation domain.
In the step 4, when the calculated domain length size with the minimum relative error is obtained, the aerodynamic effects caused by external secondary explosion, Helmholtz oscillation and Taylor instability are also simultaneously synthesized, and the calculated domain length size is finally determined.
According to the technical scheme provided by the invention, the method can provide reference basis for selecting the length and the size of the calculation domain during the gas explosion numerical simulation and acquiring the accurate explosion venting flow field, so that the prevention and control capability of the indoor gas explosion disaster is improved.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on the drawings without creative efforts.
Fig. 1 is a schematic flow chart of a method for determining a length dimension of a computational domain of an indoor combustible gas constrained explosion venting numerical value according to an embodiment of the invention;
FIG. 2 is a graph showing the overpressure time at a position 0.4m from the rear wall in the experiment according to the example of the present invention;
FIG. 3 is a diagram of a numerical computational physics model in an example embodiment of the present invention;
FIG. 4 is a schematic view of the overpressure time curve of different sized calculation domains near the center of the room (measurement point 5) according to the example of the present invention;
FIG. 5 is a schematic diagram of overpressure time curves of different size calculation domains in the vicinity of an explosion vent (measuring point 10) in a room according to an embodiment of the invention;
FIG. 6 is a schematic diagram of overpressure time curves of 3 types of calculation domains with different sizes in the vicinity of a room external constraint explosion vent (measuring point 11) according to an embodiment of the invention;
FIG. 7 is a comparison of pressure peaks near a restricted explosion vent for 4 sets of computational domains according to an embodiment of the present invention;
FIG. 8 is a graphical representation of the effect of different calculated field sizes on flame speed in accordance with an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention are clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without making any creative effort, shall fall within the protection scope of the present invention.
The following will describe an embodiment of the present invention in further detail with reference to the accompanying drawings, and as shown in fig. 1, a flow chart of a method for determining a length dimension of a computation domain of an indoor combustible gas constraint explosion venting numerical value provided by the embodiment of the present invention is schematically shown, where the method includes:
in this step, the explosion overpressure experimental data includes: peak overpressure in the chamber, maximum oscillation amplitude on the overpressure curve, overpressure curves at different locations, peak overpressure in the chamber, and flame speed.
Here, the embodiment of the present invention respectively considers the indoor peak overpressure, the maximum oscillation amplitude on the overpressure curve, the overpressure curve at different positions, the indoor peak overpressure curve, the flame speed, and other changes when the calculation domains with different dimensions are outside the explosion vent. Researches show that as the length size of a calculation domain outside an explosion relief opening is increased, the indoor peak overpressure is gradually reduced, the maximum oscillation amplitude on an overpressure time curve is increased, and the relative errors between the numerically calculated peak overpressure and maximum oscillation amplitude and experimental results are gradually reduced; meanwhile, as the length of a calculation domain outside the explosion release port is increased, the oscillation effect on an overpressure curve in a room tends to increase, but a peak overpressure curve tends to be stable; as the length of the calculation region is increased, the flame speed is reduced near the explosion venting port.
This indicates that: the size of the external calculation domain of the explosion venting port has obvious influence on the confined explosion venting of the combustible gas in the room, and when the numerical simulation method is used for researching the explosion venting of the gas in the room, the influence of the size of the external calculation domain of the explosion venting port on the explosion venting effect in the room needs to be considered, and the proper size of the external calculation domain is selected. Based on the research results, when the external numerical calculation domain size of the explosion venting port is determined, the external numerical calculation domain size needs to be considered from the angles of indoor peak overpressure, maximum oscillation amplitude on an overpressure curve, overpressure curves at different positions, indoor peak overpressure curves, flame speed and the like, a proper external calculation domain size is recommended according to each constraint explosion venting effect parameter, and then all the sizes are comprehensively compared, so that the optimal constraint explosion venting numerical calculation domain size is preferably selected.
in this example, the physical model of the room to be studied is a cuboid, whose dimensions can be expressed as:
in the formula, MroomRepresenting the dimensions of the physical model of the room; l represents the length of the room, m; w represents the width of the room, m; h denotes the height of the room, m.
The calculation domain in the physical model is a cuboid, and the size of the calculation domain can be expressed as:
in the formula, McomputationRepresenting the size of the computational domain; l represents the length of the computation domain, m; w represents the width of the computational domain, m; h represents the height of the computational domain, m.
Since the size of the calculation domain in the longitudinal direction has a large influence on the explosion, it is necessary to confirm the size of the calculation domain in the longitudinal direction in the study. And the calculation domain comprises two part sizes outside the room and the explosion vent, namely L ═ L + Lout. Thus, the computational domain size can be expressed as:
in the formula IoutIndicating the size of the calculated field outside the room vent.
In order to obtain the optimal length dimension of the outer computational domain, it is usually necessary to design a set of dimensions for the comparative analysis. In the external calculation domain size design process, the accuracy of a calculation result is improved as much as possible, and the calculation time is shortened. The invention takes m times of 1/n equal length of room length as the reference standard when selecting the external calculation domain, which can be expressed as:
in the formula, m and n are integers, and values can be flexibly selected according to the room length in the calculation process.
here, each calculation process establishes a physical model using the room model of equation (2) and the calculation domain sizes of equations (3) and (4), and performs simulation calculation.
When in calculation, a computational fluid dynamics technology is utilized, and a series of equation sets including a mass conservation equation, a momentum conservation equation, an energy conservation equation and the like are solved by adopting finite volume method numerical values, so that overpressure data are finally obtained.
in the step, the specific process is as follows:
obtaining indoor peak overpressure in different calculation domains according to the numerical simulation result, comparing the indoor peak overpressure with the indoor peak overpressure obtained in the step 1, checking relative error distribution of each group of data and the experiment result, and selecting a proper external calculation domain length size S1;
obtaining maximum oscillation amplitude values on the overpressure curve in different calculation domains according to the numerical simulation result, comparing the maximum oscillation amplitude values with the maximum oscillation amplitude values obtained in the step 1, checking the relative error distribution of each group of data and the experiment result, and selecting a proper external calculation domain length size S2;
acquiring overpressure curves in different calculation domains according to the numerical simulation result, comparing the overpressure curves with the overpressure curves obtained in the step 1, checking whether the oscillation effect on each group of data overpressure curves sufficiently shows the external aerodynamic effect, and selecting a proper external calculation domain length size S3;
obtaining peak overpressure curves near the explosion venting port in different calculation domains according to the numerical simulation result, comparing the peak overpressure curves with the peak overpressure curve obtained in the step 1, checking whether the peak overpressure curves calculated by each group of numerical values tend to be stable along with the increase of the size of the calculation domain, and selecting a proper length size S4 of the external calculation domain;
and (4) acquiring flame speeds in different calculation domains according to the numerical simulation result, comparing the flame speeds with the flame speed acquired in the step 1, and selecting a proper length size S5 of the external calculation domain.
In addition, when the calculated domain length dimension with the minimum relative error is obtained, the aerodynamic effects brought by external secondary explosion, Helmholtz oscillation and Taylor instability are also simultaneously synthesized, and the calculated domain length dimension l is finally determinedout。
Specifically, the length dimension l of the external calculation domain of the explosion vent is determined by comprehensively comparing the length dimensions S1 to S5 of the external calculation domainoutAdding the length dimension L of the room to be studied to obtain the length dimension L of the whole calculation domainout+l。
The above determination method is explained in detail below by specific examples, assuming that the size of the gas explosion room to be measured is 9m × 4.5m × 4.5m, and four groups of different explosion and leakage products (20.25 m) are analyzed2、10.13m2、5.06m2And 2.25m2) And 14 explosion venting effects distributed by different barriers, wherein the opening pressure of an explosion venting port is 2.6kPa, and the pressure in a room and a flame measuring point are positioned on the floor of the room in the experiment.
FIG. 2 shows the position 0.4m away from the back wall in the experiment according to the example of the present inventionThe pressure-time curve is shown schematically, and the corresponding pressure-explosion opening volume is 2.25m2And explosive conditions with a volume blockage of 0%. It can be seen that: two obvious peaks are arranged on the overpressure curve, the first peak P1The second peak pressure corresponds to the opening moment of the explosion vent, corresponds to the external explosion and presents a series of oscillation peaks, mainly caused by Helmholtz oscillations and Taylor instability, when the peak overpressure of the room is 35.3 kPa.
According to the general characteristics of the gas explosion intensity disaster in the common room, and in order to compare with the large-scale natural gas explosion venting experiment result, the physical model size calculated by the numerical value adopted in the example is 9m multiplied by 4.5m, and the area is 2.25m2The explosion venting port is arranged at the geometric center of one vertical wall body, and the opening pressure of the explosion venting port is 2.6kPa, so that the explosion venting port is the same as the parameters of an explosion chamber in an experiment. The ignition source is positioned at the geometric center of the rear wall of the room, is 0.1m away from the rear wall, and has the radius of 0.015 m. Since the main component of natural gas is methane, in this example, a methane/air mixed gas with a methane volume concentration of 9.5% is used as a detonation source, the methane/air is uniformly mixed at the time of ignition and is in a static state, and the initial pressure and the initial temperature of the environment in the calculation domain are respectively set to be 1.01325 × 105Pa and 300K. The example uses a 0.1m size structural grid based on the grid size used in performing calculations using computational fluid dynamics techniques in similar studies.
FIG. 3 is a schematic diagram of a numerical calculation physical model in an example of the invention, in which a measuring point is located at the geometric center of the cross section of the model, a measuring point 1 is located at 0.5m on the X axis, and measuring points 2 to 9 are respectively located at 1m to 8m on the X axis at an interval of 1 m; the measuring points 10 and 11 are respectively positioned at two sides of the explosion venting port on the X axis and are respectively 0.2m away from the explosion venting port, and the other measuring points are respectively positioned at 9.5m to 17.5m away from the X axis at an interval of 1 m.
In order to analyze the influence rule of the length of the calculation domain outside the explosion venting port of the room on the overpressure of the indoor explosion, the embodiment respectively examines that the lengths L of the calculation domain are respectively 9m, 12m, 15m and 18m (an explosion venting port external meter)Length of computation field loutRespectively 0m, 3m, 6m and 9m), the dimensions in the Y direction and the Z direction of the whole calculation domain are kept unchanged in the test process, namely 4.5 m. The space of the calculation domain outside the explosion venting port of the room is set as a free opening boundary in other directions except that the ground is rigid.
In the concrete implementation, when the indoor natural gas constraint explosion venting is calculated by adopting a numerical method, in order to select a proper external calculation domain size, the influence of different calculation domain length sizes outside the explosion venting port on the indoor constraint explosion venting effect is explored from the aspects of indoor peak overpressure, maximum oscillation amplitude on an overpressure curve, overpressure curves at different positions, an indoor peak overpressure curve, flame speed and the like, specifically:
(1) peak indoor overpressure
When the area of the explosion venting port is 2.25m2The peak overpressure in the room at a position 0.4m from the rear wall was 35.3 kPa. The peak overpressure at 0.4m from the back wall in the room and the relative error from the experimental results (35.3kPa) of 4 sets of calculation domains with different sizes are shown in the following Table 1, and it can be seen from the Table 1 that the relative error from the experimental results of each set of data is within 10%, and when the length l of the calculation domain outside the explosion vent is larger than loutThe relative error is less than 5% when the distance is 3m and 9m, which shows that when the length of the calculation domain outside the explosion venting port is 3m or 9m, the indoor peak value is more reasonable.
TABLE 1 Peak overpressure at different outer calculation domains and relative error compared to experimental results (35.3kPa)
(2) Maximum oscillation amplitude on overpressure curve
Due to the effect of the aerodynamic oscillation effects, in addition to the peak overpressure, consideration is also requiredAnd constraining the maximum oscillation amplitude of the overpressure curve in the explosion venting process, filtering the overpressure curve obtained by experiments and numerical calculation to obtain a smooth overpressure curve, comparing the smooth overpressure curve with the unfiltered overpressure curve, and calculating to obtain the maximum oscillation amplitude on the overpressure curve. In the above-mentioned room gas explosion venting experiment, when the explosion venting volume is 2.25m2The maximum oscillation amplitude at a position 0.4m from the rear wall in the room was 3.113 kPa. The maximum oscillation amplitude of 4 sets of differently sized computational domains at a position 0.4m from the rear wall in the room and the relative error from the experimental results (3.113kPa) are shown in table 2 below, and the results show that: as the calculated area outside the vent increases, the maximum oscillation amplitude in the chamber also increases. When calculating the field length l externallyoutAt 9m, the relative error was 24.78%. At the moment, the oscillation value is more reasonable when the calculation domain outside the explosion venting port is 9 m.
TABLE 2 maximum oscillation amplitude at different outer calculation domains and relative error compared to experimental results (3.113kPa)
(3) Overpressure time curves at different positions in room
Fig. 4 is a schematic diagram of overpressure time curves of different size calculation domains near the center of a room (measuring point 5) according to the embodiment of the invention, and it can be seen from fig. 4 that: when the external calculation domain of the explosion relief opening is 0m, the overpressure time curve is a smooth curve, and the pressure peak value is only P1And P2There is no pressure oscillation caused by the gas flow. While the other sets of calculation domains have pressure peaks P1The size is basically the same, but as the length of a calculation domain outside a room explosion vent is increased, the pressure peak value P2A slight decrease is present and the phenomenon of aerodynamic oscillations on the overpressure curve is more pronounced. This is probably because when there is a computational domain outside the room explosion vent, the aerodynamic effects of external secondary explosion, Helmholtz oscillation, and Taylor instability, etc. formed during the gas containment explosion vent, affect the overpressure curve in the room.
Fig. 5 is a schematic diagram showing the overpressure time curve of the calculation domain of different sizes in the vicinity of the explosion vent (measuring point 10) in the room according to the embodiment of the invention, and it can be seen from fig. 5 that: the overpressure time curve without the external calculation domain is smooth, and other three groups of overpressure curves have obvious overpressure oscillation peaks. At the pressure peak P1Then, the pressure curve suddenly drops and a small oscillation occurs, because this point is at the edge of the vent, affected by the opening of the vent and the Helmholtz oscillation phenomenon caused by the gas flow. At the pressure peak P2Then, the overpressure curve exhibits a relatively strong oscillation around the equilibrium pressure, and the amplitude of the overpressure curve increases with increasing outer calculation field.
Fig. 6 is a schematic diagram showing overpressure time curves of 3 types of calculation domains with different sizes in the embodiment of the invention in the vicinity of the room outside constraint explosion vent (measuring point 11), and as can be seen from fig. 6: there are also two distinct pressure peaks on the pressure time curve. Pressure peak P1The same is true. Pressure peak P3Basically the same, but as the size of the calculation domain outside the explosion vent increases, the oscillation amplitude of the measuring point outside the room also increases. Therefore, in order to fully consider the influence of gas dynamic effects such as secondary explosion outside the natural gas explosion, Helmholtz oscillation, Taylor instability and the like on indoor overpressure, the calculation domain outside the explosion relief opening is recommended to be 9 m.
(4) Peak overpressure curve in room
FIG. 7 is a diagram showing a comparison of pressure peaks near the restricted explosion vent for 4 sets of computation domains according to the example of the present invention, and it can be seen from FIG. 7 that: in the same calculation domain, the peak overpressure shows an obvious descending trend along with the closer the measuring point is to the explosion venting port. And among different calculation domains, the peak overpressure of each point presents a descending trend along with the increase of the size of the calculation domain outside the explosion vent. And 3 peak overpressure curves with the sizes of the external calculation domains of the explosion relief opening being 3m multiplied by 4.5m, 6m multiplied by 4.5m and 9m multiplied by 4.5m are basically overlapped in the room, which shows that the influence of the sizes of the external calculation domains of the explosion relief opening on the internal peak overpressure tends to be stable, so the length size l of the external calculation domains of the explosion relief opening tends to be stableout3m, 6m and 9m all meet the requirements.
(5) Analysis of the effects of indoor flame speed
The propagation speed of the flame in the room is obtained by calculating the temperature curve in the room, and particularly, the moment when the flame reaches a certain point is assumed to be equal to the moment when the temperature rising rate at the point is maximum, and the flame front can be considered to reach the position. Flame speed is the result of the interaction of the combustion rate with the induced flow rate, which affects flame speed much more for turbulent explosion venting, and the combustion produces pressure, which induces gas flow, and any change in the outflow velocity will have a significant effect on flame speed.
FIG. 8 is a schematic diagram illustrating the effect of different calculated domain sizes on flame speed according to an embodiment of the present invention, as can be seen from FIG. 8: flame speed increases with increasing propagation distance and the trend of flame speed within 5m of the ignition source for each set of calculation domains is substantially consistent. This is because there are no obstructions in the model of each of the composition examples, and the size of the explosion vents and the opening pressure in the rooms are the same, so that the flame speed variation caused by the induced flow velocity in each of the rooms is substantially the same. But the flame speed value is fluctuated beyond 5m from the ignition source, because the measuring points are close to the explosion venting port, and the measuring points are influenced by factors such as the opening of the explosion venting port, Helmholtz oscillation, Taylor instability effect and the like, the turbulence intensity of a flow field is increased, and the induced flow rate is forced to change. As the calculated field outside the vent increases, the flame speed at 8m shows a downward trend, which is related to the induced flow field in the room. From the results of the foregoing analysis, it can be seen that as the calculated area outside the explosion vent increases, the peak overpressure in the room tends to decrease, resulting in a slower induced flow rate, thereby reducing the flame speed. Thus, in view of the trend of the flame propagation speed, in order to take into account the effect of aerodynamic effects, the length dimension l of the calculation region outside the explosion venting opening is recommendedoutIs 9 m.
From the results of the above example it can be seen that: in the example, the change conditions of indoor peak overpressure, maximum oscillation amplitude on an overpressure curve, overpressure curves at different positions, indoor peak overpressure curves, flame speed and the like in different calculation domains outside the explosion relief port are respectively inspected, and comparative analysis is carried out on the change conditions and the experimental results. Researches show that as the size of a calculation domain outside an explosion relief opening increases, the indoor peak overpressure shows a gradual reduction trend, the maximum oscillation amplitude on an overpressure time curve increases, and the relative errors between the numerically calculated peak overpressure and maximum oscillation amplitude and experimental results gradually decrease; meanwhile, as the length of a calculation domain outside the explosion venting port is increased, the oscillation effect on an overpressure curve in a room is increased, but a peak overpressure curve is stable; as the length of the calculation region is increased, the flame speed is reduced near the explosion venting port.
Therefore, when the size of the numerical calculation domain outside the explosion venting port is determined, the proper size of the external calculation domain is recommended according to each constraint explosion venting effect parameter by considering the angles of indoor peak overpressure, maximum oscillation amplitude on an overpressure curve, overpressure curves at different positions, indoor peak overpressure curves, flame speed and the like, and the optimal size of the constraint explosion venting numerical calculation domain is optimized by comprehensively comparing the sizes.
It is noted that those skilled in the art will recognize that embodiments of the present invention are not described in detail herein.
In summary, the method provided by the embodiment of the invention can provide reference basis for selection of the length and the size of the calculation domain during the gas explosion numerical simulation and acquisition of the accurate explosion venting flow field, thereby improving the prevention and control capability of indoor gas explosion disasters.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (3)
1. A method for determining the length and the size of an indoor combustible gas constraint explosion venting numerical calculation domain is characterized by comprising the following steps:
step 1, explosion overpressure experimental data with a scale similar to that of a numerical research model is obtained through experiments or literature investigation;
step 2, establishing a physical model for restricting explosion venting by using numerical simulation software, and designing calculation domains with different length sizes outside an explosion venting port according to the size of a room to be researched for carrying out numerical analysis;
in the step 2, the process of establishing the constrained explosion venting physical model specifically comprises the following steps:
the physical model of the room to be studied is set as a cuboid, the dimensions of which are expressed as:
in the formula, MroomRepresenting the dimensions of the physical model of the room; l represents the length of the room; w represents the width of the room; h represents the height of the room;
the computational domain size is then expressed as:
in the formula, McomputationRepresenting a computational domain size; loutRepresenting the size of a calculation domain outside a room explosion vent; w represents the width of the computational domain; h represents the height of the computational domain;
in each calculation process, a constrained explosion venting physical model is established by utilizing a room model and the size of a calculation domain, and simulation calculation is carried out;
the method comprises the following steps of designing calculation domains with different lengths and sizes outside an explosion venting port according to the size of a room to be researched for carrying out numerical analysis, and specifically comprises the following steps:
taking m times of 1/n equal length of room length as a reference standard when selecting an external calculation domain, specifically expressed as:
in the formula, m and n are integers, and values are flexibly taken according to the length of a room in the calculation process;
step 3, carrying out numerical simulation by using the established constraint explosion venting physical model, and respectively obtaining related explosion overpressure experimental data under calculation domains with different length sizes;
step 4, comparing the data result obtained in the step 3 with the experimental data result obtained in the step 1 to obtain the length size of the calculation domain with the minimum relative error, wherein the specific process is as follows:
obtaining indoor peak overpressure in different calculation domains according to the numerical simulation result, comparing the indoor peak overpressure with the indoor peak overpressure obtained in the step 1, checking relative error distribution of each group of data and the experiment result, and selecting a proper external calculation domain length size S1;
obtaining maximum oscillation amplitude values on the overpressure curve in different calculation domains according to the numerical simulation result, comparing the maximum oscillation amplitude values with the maximum oscillation amplitude values obtained in the step 1, checking the relative error distribution of each group of data and the experiment result, and selecting a proper external calculation domain length size S2;
acquiring overpressure curves in different calculation domains according to the numerical simulation result, comparing the overpressure curves with the overpressure curves obtained in the step 1, checking whether the oscillation effect on each group of data overpressure curves sufficiently shows the external aerodynamic effect, and selecting a proper external calculation domain length size S3;
obtaining peak overpressure curves near the explosion venting port in different calculation domains according to the numerical simulation result, comparing the peak overpressure curves with the peak overpressure curve obtained in the step 1, checking whether the peak overpressure curves calculated by each group of numerical values tend to be stable along with the increase of the size of the calculation domain, and selecting a proper length size S4 of the external calculation domain;
acquiring flame speeds in different calculation domains according to the numerical simulation result, comparing the flame speeds with the flame speed acquired in the step 1, and selecting a proper length size S5 of the external calculation domain;
step 5, determining the length dimension l of the external calculation domain of the explosion venting port according to the length dimension of the calculation domain obtained in the step 4outIn addition to waitingThe length dimension L of the room is studied, and the length dimension L of the entire calculation field is obtainedout+l。
2. The method of claim 1, wherein the experimental data of explosion overpressure comprises:
peak overpressure in the chamber, maximum oscillation amplitude on the overpressure curve, overpressure curves at different locations, peak overpressure in the chamber, and flame speed.
3. The determination method as claimed in claim 1, wherein in the step 4, when the calculated domain length dimension with the minimum relative error is obtained, the aerodynamic effects caused by external secondary explosion, Helmholtz oscillation and Taylor instability are simultaneously synthesized, and the calculated domain length dimension is finally determined.
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